| Message ID | 20200507190223.GA15428@embeddedor (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | NFS: Replace zero-length array with flexible-array | expand |
diff --git a/include/linux/nfs4.h b/include/linux/nfs4.h index 82d8fb422092..7c4b63561035 100644 --- a/include/linux/nfs4.h +++ b/include/linux/nfs4.h @@ -38,7 +38,7 @@ struct nfs4_ace { struct nfs4_acl { uint32_t naces; - struct nfs4_ace aces[0]; + struct nfs4_ace aces[]; }; #define NFS4_MAXLABELLEN 2048 diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h index 440230488025..6aad9b0a5062 100644 --- a/include/linux/nfs_xdr.h +++ b/include/linux/nfs_xdr.h @@ -1227,7 +1227,7 @@ struct nfs4_secinfo4 { struct nfs4_secinfo_flavors { unsigned int num_flavors; - struct nfs4_secinfo4 flavors[0]; + struct nfs4_secinfo4 flavors[]; }; struct nfs4_secinfo_arg {
The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues. This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> --- include/linux/nfs4.h | 2 +- include/linux/nfs_xdr.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)